Features of Object Oriented Programming

Features of Object Oriented Programming

There are various characteristics of object oriented programming and those are -

1) Abstraction

2) Object and Classes

3) Encapsulation

4) Inheritance and

5) Polymorphism.

Abstraction

Definition: Abstraction means representing only essential features by hiding all the implementation details. In object oriented programming languages like C++, or Java class is an entity used for data abstraction purpose.

Example

class Student

{

int roll;

char name [10];

public;

void input ();

void display();

}

In main function we can access the functionalities using object. For instance

Student obj;

obj.input();

obj.display ();

Thus only abstract representation can be presented, using class.

Object

• Object is an instance of a class.

• Objects are basic run-time entities in object oriented programming.

• In C++ the class variables are called objects. Using objects we can access the member variable and member function of a class.

• Object represent a person, place or any item that a program handles.

• For example - If the class is country then the objects can be India, China, Japan, U.S.A andso on.

• A single class can create any number of objects.

• Declaring objects -

The syntax for declaring object is -

Class Name Object_Name;

• Example

Fruit f1;

For the class Fruit the object f1 can be created.

Classes

• A class can be defined as an entity in which data and functions are put together.

• The concept of class is similar to the concept of structure in C.

• Syntax of class is as given below

class name_of_class

{

private:

variables declarations; function declarations;

public:

variable declarations;

function declarations;

}; do not forget semicolon

•Example

class rectangle

{

private :

int len, br;

public:

};

void get_data();

void area();

void print_data ();

• Explanation

o The class declared in above example is rectangle.

o The class name must be preceded by the keyword class.

o Inside the body of the class there are two keywords used private and public. These are called access specifiers.

Encapsulation   

• Encapsulation is for the detailed implementation of a component which can be hidden from rest of the system.

• In C++ the data is encapsulated.

• Definition: Encapsulation means binding of data and method together in a single entity called class.

• The data inside that class is accessible by the function in the same class. It is normally not accessible from the outside of the component.

Inheritance

•  Definition: Inheritance is a property by which the new classes are created using the old classes. In other words the new classes can be developed using some of the properties of old classes.

•  Inheritance support hierarchical structure.

•  The old classes are referred as base classes and the new classes are referred as derived classes. That means the derived classes inherit the properties (data and functions) of base class.

• Example: Here the Shape is a base class from which the Circle, Line and Rectangle are the derived classes. These classes inherit the functionality draw() and resize(). Similarly the Rectangle is a base class for the derived class Square. Along with the derived properties the derived class can have its own properties. For example the class Circle may have the function like backgrcolor() for defining the back ground color.

Polymorphism

•  Polymorphism means many structures.

•  Definition: Polymorphism is the ability to take more than one form and refers to an operation exhibiting different behavior in different instances (situations).

• The behavior depends on the type of data used in the operation. It plays an important role in allowing objects with different internal structures to share the same external interface. Without polymorphism, one has to create separate module names for each method.

•  For example the method clean is used to clean a dish object, one that cleans a car object, and one that cleans a vegetable object.

•  With polymorphism, you create a single "clean" method and apply it for different objects.